1. Field of the Invention
The present general inventive concept relates to an image heating apparatus, and more particularly, to a method and apparatus to fuse an image, which can reduce a warm-up time and also can improve a fusing quality.
2. Description of the Related Art
An image heating apparatus generally includes a heating roller and a pressure roller. The image heating apparatus may pass a printing paper, formed with an image, through the heating roller and the pressure roller and thereby fuse the image on the printing paper. Accordingly, the image heating apparatus may be used for a copying machine, a printer, a facsimile, and the like. Also, the image heating apparatus may be used to fuse character or image information on a printing paper as an image.
A main task of the image heating apparatus may be to fuse an image identical to an original image on the printing paper. Also, the image heating apparatus may reduce an initial warm-up time and power consumption.
FIG. 1 is a cross-sectional view illustrating a conventional printer, and FIG. 2 is an enlarged cross-sectional view illustrating a conventional image heating apparatus 100 in the printer of FIG. 1. The image heating apparatus 100 shown in FIGS. 1 and 2 is disclosed in U.S. Pat. No. 5,148,226, issued on Sep. 15, 1992.
Referring to FIG. 1, the printer may be, for example, a laser beam printer having a housing 65. The printer includes a processing cartridge 60. Also, the processing cartridge 60 includes a rotating drum 61, a charger 62, a developing device, and a cleaning device. The processing cartridge 60 is mounted to be separable from the printer when a cover 65 is open.
When the printer is operating, the rotating drum 61 rotates along an arrow direction shown in FIG. 1, that is, rotates clockwise. A surface of the rotating drum 61 is uniformly charged by the charger 62 and exposed to a scanning laser beam 67. In this instance, the scanning laser beam 67 is scanned from a laser scanner 66, and is controlled in correspondence to image information to be recorded. Accordingly, the rotating drum 61 defines an electrostatic latent image. In this instance, the latent image is developed into a toner image while passing through a toner storage unit 63.
In this instance, one sheet of a printing paper P is supplied from a cassette 68. While the printing paper P is passing through the rotating drum 61 and an image transfer roller 72, the toner image is transferred from the rotating drum 61 to the printing paper P. Also, the surface of the rotating drum 61 is cleaned while passing through a cleaning member 64. In this instance, contaminants remaining on the surface of the rotating drum 61 may be removed. The printing paper P with the formed toner image moves to the image heating apparatus 100. the printing paper P fed along paths 71, 73, 74, and 75.
Referring to FIG. 2, the image heating apparatus 100 includes a pressure roller 10, a fixed structure 13, an insulating member 20, a heater 19, and a film 21. The fixed structure 13 is fixed in the image heating apparatus 100. Also, the fixed structure 13 includes front and rear walls 15 and 16 to guide the film 21, and a middle portion connected between the front and rear walls 15 and 16. The heater 19 and the insulating member 20 are provided on the middle portion in a lower portion of the fixed structure 13. The film 21 is formed in a shape of a belt, and contains the fixed structure 13 and the heater 19 and thereby rotates. The paper P with a toner image Ta passes through a region N corresponding to the heater 19 such that the toner image Ta is fused as a fused image Tb and then discharged using a guide 33 and rollers 34 and 35. When the film 21 rotates in a direction A, a pressure f is exerted in a region B.
The fixed structure 13 and the heater 19 are formed in a solid body. Also, the fixed structure 13 and the heater 19 may simultaneously move up and down above the pressure roller 10. Accordingly, the fixed structure 13 and the heater 19 may contact the printing paper P on the same plane exclusively and at all times.
Also, since the fixed structure 13 and the heater 19 may contact each other along the lengthwise direction with the same characteristics, it may be impossible to change a nip characteristic along the lengthwise direction of the pressure roller 10. In this instance, when the pressure roller 10 is formed in a simple cylindrical shape, pressure is irregularly distributed in a nip formed between the pressure roller 10 and the film 21. A central portion based on the pressure roller 10 has greater pressure than the pressure in margin portions, which are provided in both ends. Accordingly, as disclosed in U.S. Pat. No. 5,148,226, the pressure roller 10 is formed in a shape of a reverse-crown, so that the central portion may have substantially identical pressure as the pressure in margin portions.
Also, in the fixed structure 13 in which the heater 19 is fixed, the heater 19 may directly transfer pressure from the pressure roller 10 and the printing paper P. Accordingly, when greater pressure is applied to the heater 19, some damage may be inflicted on the surface of the heater 19, although a bottom surface of the heater 19 is protected by a surface protecting layer.
Therefore, the conventional method and apparatus cannot reduce a warm-up time and improve a fusing quality when fusing the image.